Timed decision load control system



Aug. 4, 1970 L. K. CLARK ET L 3,

TIMED DECISION LOAD CONTROL S YSTEM FIG. 2

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ATTORN EYS L L. K. CLARK ET AL TIMED DECISION LOAD CONTROL Aug. 4, 1970SYSTEM 5 Shets-Sheet 5 Filed Oct. 12, 1966 7 76 ADD A.C.TO D.C.CONVERTER J COMPARATOR I PASSAGE TIME TlMER "3;""" """1 I +Vl V0 I I Ei1 ?E I d TIME WAITING-MINIMUM LuLL INVENTORS- LARRY K. CLARK a FRANK; w.HILL Amo 0.0. CONVtHItH :W 8+ I02 ||O-\ RAND 6 M \I04 TIMER FIG. 3A

ATTORNEYS Aug. 4, 1970 L. K. CLARK T TIMED DECISION LOAD CONTROL SYSTEM5 Sheets-Sheet 4 Filed Oct. 12. 1966 Ll (ExcEPT DURING STEP POSITIONS 3AND) ,8)

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ATTORNEYS 3,522,581 Patented Aug. 4, 1970 US. Cl. 340-37 15 ClaimsABSTRACT OF THE DISCLOSURE A load control system is disclosed hereinwhich is particularly applicable to traffic controllers. Specifically, atrafiic controller is disclosed which incorporates a minimum initialtimer, a variable initial timer, and a unit extension timer. Circuitryis provided for concurrently energizing the three timers so that theyall commence their timing functions at substantially the same point intime. In this manner, and especially during light traffic conditions,the unit extension timer may have at least partially completed itstiming function prior to the point in time that the minimum initial andvariable initial timers have completed their timing functions.

DISCLOSURE This invention relates to the art of timing and moreparticularly, to a plurality of timers which may time concurrently tocontrol energization of a load.

The invention is particularly applicable in conjunction with trafiiccontrol and will be described with particular reference thereto;although, it is to be appreciated that the invention may be used, forexample, in conjunction with timed control of conveyor systems or timedcontrol of industrial processes.

A trafiic actuated controller serves to control the operation of atraffic intersection signal displaying go, caution and stop signals totwo or more intersecting traflic phases in accordance with trafficdemand as registered with the controller by vehicle detectors in thetraffic actuated phases. Traffic actuated controllers, eithersemiactuated or full actuated, known heretofore have included, for eachtraflic actuated phase, a minimum initial timer, a variable initialtimer, a vehicle extension timer, and an extension limit timer.

A minimum initial timer serves to time a predetermined minimum period ofgo time to permit a given number of vehicles in the actuated tratiicphase to commence movement through the intersection. A variable initialtimer serves to time an adjustable period of go time dependent on thenumber of vehicles detected in the actuated phase during the previousperiod of time that a stop signal was displayed to that phase. Aresettable vehicle extension timer serves to time at least oneadditional-increment of go time, known as a vehicle extension period,with the vehicle extension period being sufficient to permit the vehicleto travel from the detector in the actuated phase to the stop line. Thevehicle extension timer is reset by each vehicle detected in theactuated phase once a go signal has been displayed to that phase. Anextension limit timer, sometimes referred to as a maximum timer, servesto time a maximum allowable period of go time for the actuated phase.Normally, the minimum initial and variable initial timers are initiallyenergized at the same time so that they may commence their timingfunctions concurrently, with the last to time out serving to provide acontrol signal for initiating termination of an initial go interval forthe actuated phase. The unit extension timer is then energized to timeat least one additional increment of go time for the actuated phase.

A notatable problem with such traffic controllers, as described above,occurs during light traffic conditions. More particularly, when traflicvolume is light both the minimum initial and variable initial timersmust time out before the unit extension timer can commence its timingfunction. Accordingly, under such. light trafiic conditions there may beno need to provide an additional increment of go time during the vehicleextension period and, hence the allocation of such go time constitutesan unnecessary waste of go time being allocated to the associatedtraffic actuated phase.

The present invention is directed toward circuitry particularlyapplicable for use with traffic controllers so that the minimum initial,variable initial, and unit extension timers concurrently time theirrespective timed intervals, whereby during light traffic conditions theunit extension timer may have at least partially completed its timingfunction prior to the point in time that the minimum initial andvariable initial timers have completed their timing functions, therebyovercoming the noted disadvantages and others of previous trafliccontrollers.

In accordance with one aspect of the present invention, it iscontemplated that a controller serves to control stop and go movement ofmovable means, such as Vehicles, through an intersection of at least twoflow paths, such as trafiic phases, of movement of the movable means andwherein at least one of the paths has detection means associatedtherewith for detecting each said movable means in the associated path.

More particularly, the controller includes for each flow path: firsttiming means, such as minimum initial timing means for timing apredetermined .minimum go signal initial interval, and then developing afirst signal; second timing means, such as variable initial timing meanscontrolled by the associated detection means for timing a variable gosignal initial interval in accordance with the number of vehiclesdetected by the detection means during the preceding period of time thata stop signal is displaced to an actuated phase, and then developing asecond signal; third timing means, such as vehicle extension timingmeans for timing at least a predetermined vehicle extension period oftime, and then developing a third signal; starting means for initiallyand concurrently energizing the first, second and third timing means sothat all of these timing means commence their timing functions atsubstantially the same point in time; AND circuit means for developingan initial interval termination signal only when both the first andsecond signals have been developed; second AND circuit means responsiveto the initial interval termination signal and the third signal fordeveloping an extension interval termination signal only when both theinitial termination signal and the third signal have been developed;and, interval control means responsive to the interval terminationsignals for terminating the initial go interval in response to theinitial interval termination signal and terminating the vehicleextension interval in response to the extension interval terminationsignal.

In accordance with a still further aspect of the present invention, thetraflic controller includes reset means controlled by the associateddetection means for resetting the vehicle extension timing means inresponse to each detection of a vehicle in the actuated phase so thatthe vehicle extension timing means commences to time another vehicleextension period.

In accordance with a still further aspect of the present invention, thecontroller includes extension limit timing means for timing apredetermined time limit for the go signal displayed to the actuatedphase, and then developing a fourth signal; and, reset disabling meansresponsive to the fourth signal for disabling the reset means, wherebythe vehicle extension timer means completes its timing function, andthen develops the third signal.

The primary object of the present invention is to provide improvedcircuitry for energizing several timers so that they time togetherconcurrently for energizing a load.

A still further object of the present invention is to provide timingcircuitry which is relatively simple in manufacture and economical inoperation.

A still further object of the present invention is to provide animproved traffic controller wherein various timing periods timed by thecontroller are timed concurrently.

A still further object of the present invention is to provide animproved traffic controller for minimizing wasted right-of-way timeduring an operation cycle.

A still further object of the present invention is to provide animproved trafiic controller wherein the vehicle extension timer may timeconcurrently with the variable initial and minimum initial timers.

The foregoing and other objects and advantages of the invention willbecome apparent from the following description of the preferredembodiment of the invention as read in connection with the accompanyingdrawings in which:

FIG. 1 is a schematic illustration of a typical intersection to whichthe present invention may be applied;

FIG. 2 is a block diagram of the preferred embodiment of the invention;

FIGS. 3, 3A and 3B, taken together, is a single figure of a blockdiagram of a traific controller incorporating the preferred embodimentof the invention illustrated in FIG. 2; and,

FIG. 4 is a chart illustrating trafiic intervals corresponding with stepswitch positions.

Referring now to the drawings, and more particularly to FIG. 2, there isshown a preferred embodiment of the invention for controlling theoperation of load L, such as a step switch driver coil in a trafficcontroller, wherein the circuit generally comprises a starter C, timersT1, T2, T3, T4 and a secondary starter E. Timers T1, T2, T3 and T4 maytake various forms, such as electromechanical timers or electronictimers, such as RC unijunction relaxation oscillator circuits.

As shown in FIG. 2, timer T1 has its input circuit connected to starterC, and its output circuit connected to an AND circuit 12. Timer T2,which times in parallel with timer T1, has its input circuit connectedto starter C, and its output circuit connected to the input circuit ofAND circuit 12. The input circuit of timer T2 is also connected tostarter C through a time add disable circuit 14 and a time add circuit16. Time add disable circuit 14 is connected with an external resetcircuit 18, which in turn is connected to the input circuit of timer T3through a reset disable circuit 20. The input circuit of timer T3 isalso connected to starter C and the output circuit of the timer isconnected to the input circuit of an AND circuit 22. AND circuit 12 hasits output circuit connected to the circuit of an OR circuit 24, as wellas to an input circuit of AND circuit 22, which in turn has its outputcircuit connected to the input circuit of OR circuit 24. Timer T4 hasits input circuit connected through an AND circuit 26 to starter C andsecondary starter E, and its output circuit connected to the resetdisable circuit 20. The secondary starter E also has its output circuitconnected to an input circuit of AND circuit 22.

OPERATION Starter C applies a start signal to energize timers T1, T2,and T3. Each of these timers times its time delay period and thendevelops an output signal, such as a positive potential. Timer T1 timesa predetermined minimum initial period of time before developing anoutput signal.

In traflic control applications this timer may be a normal timer fortiming a vehicle minimum initial interval. Timer T2 serves to time avariable period of time in accordance with the number of output pulsesfrom the external reset circuit 18. Thus, for each external reset pulse,one increment of time is added to timer T2 through the time add disablecircuit 14 and the time add circuit 16. The total period of time timedby timer T2 may be less than or greater than the fixed period of timewhich is timed by timer T1. When both timers T1 and T2 have completedtheir timing functions, an output signal is developed by AND circuit 12.This output signal, Which may be considered as a binary (1) signal, isapplied through OR circuit 24 to energize load L. Similarly, this outputsignal is also applied as one of the inputs to AND circuit 22.

Timer T3 serves to time at least one fixed interval of time and thendevelop a third output signal. This timer may serve as a resettablevehicle extension timer for traffic applications. The timer is reset byeach output pulse from external reset circuit 18 through the resetdisable circuit 20. For traffic purposes, the external reset circuit maytake the form of a vehicle detector circuit. When timer T3 times out, itdevelops an output signal for application to the input circuit of ANDcircuit 22. However, an output signal is not present on the outputcircuit of AND circuit 22 until an input signal is applied to the thirdinput circuit of the AND circuit itself.

Timer T4 commences its timing function only when supplied with startsignals from starters C and E. A start signal from starter B providesthe third input signal for AND circuit 22. In the event, however, thattimer T3 has not completed its timing function, such as due to it beingconstantly reset by external reset pulses, timer T4 times apredetermined fixed period of time and develops an output signal fordisabling the reset disable circuit 20. For traific applications, timerT4 may take the form of an extension limit timer. When the reset disablecircuit 20 is disabled, timer T3 can no longer be reset and, hence, itcompletes its timing function and develops an output signal forapplication to AND circuit 22. Since all three inputs are now applied tothe AND circuit 22, an output signal is developed on its output circuitfor application through OR circuit 24 to energize load L.

Having now generally described the preferred embodiment of theinvention, attention is directed to the following detailed descriptionof the invention as applied to a traflic controller.

TRAFFIC CONTROLLER Referring now to FIGS. 1, 3 and 4 wherein theshowings are for purposes of illustrating a preferred embodiment of theinvention only, and not for limiting same, there is illustrated in FIG.1 a typical intersection of two trafiic phases, phase A and phase B.Adjacent the intersection of the two phases there is schematicallyillustrated stop lines SL which may be located as desired by municipaltraffic engineers. At each aproach to the intersection there is provideda detector, i.e., detectors D1 and D2 for the app-roaches of phase A,and detectors D3 and D4 for the approaches of phase B. Detectors D1, D2,D3 and D4 preferably take the form of loop detectors, which are wellknown in the art of traflic control, and generally comprise a closedwire loop embedded in a roadway, with the loop configuration defining anarea under surveilance by the detector, which together with associatedcircuitry develops an output signal so long as a vehicle is presentwithin the area under surveilance. Alternatively, detectors D1, D2, D3and D4 may take the form of other detectors, such as overhead mounteduntrasonic detectors which, in a manner similar to that of loopdetectors, serve to monitor or survey a predetermined area on theroadbed for the presence of vehicles and provide an output signal aslong as a vehicle is present in the area under surveilance. Further, thedetectors may also take the form of spot detectors, such as the familiartread pad, which together with its associated circuitry provides anoutput signal in response to each actuation by a vehicle momentarilypassing over the spot detector. In the event that the detectors take theform of loop detectors, as shown in FIG. 1, it is preferably that eachdetector, as illustrated with respect to detector D3 in FIG. 1, have awidth w which is sufficiently wide to detect vehicles in all of thelanes in the approach to the intersection; a length l which extends inthe direction of the phase for a distance less than the length of onevehicle, such as, for example, on the order of four feet; and, belocated at a distance a from the stop line, which distance may be on theorder of twohundred feet. The detectors D1, D2, D3 and D4 are connectedto a local controller LC, which controls the operation of anintersection trafiic signal S which displays go, caution and stopsignals to phases A and B. Preferably, in accordance with the presentinvention, loop detectors D1 and D2 are connected to a phase controlunitA for controlling the signal displays by traflic signal S to phase Aand detectors D3 and D4 are connected to phase control unit B forcontrolling the signal displays by trafiic signal S to phase B.

The traffic controller to be described hereinafter takes the form of atwo phase, full actuated, trafiic controller including a phase controlunit for each traffic phase. The invention is not limited to such atraflic controller but may be used with other controllers, such as, forexample, a semiactuated, two phase, trafiic controller or a two or morephase, full actuated, trafiic controller wherein all of the controlcircuitry is included within a given unit as opposed to phase controlunits described with reference to FIG. 3.

As shown in FIG. 1, local controller LC includes two phase control unitsA and B for respectively controlling phase A and phase B trafi'ic flow.Phase control units A and B are substantially identical and,accordingly, only phase unit A is described hereinafter in detail, itbeing understood that the description applies equally to phase unit B.

Referring now to FIG. 3, phase unit A generally cornprises five timers;namely, a normal timer T1, a variable initial timer T2, a passage timetimer T3, an extension and green No. 2 timer T4, and a timewaiting-minimum lull timer T5; and, an eight bank, eleven position stepswitch SS for controlling the operation of the phase A signal lights oftrafiic signal S through load relays LR in response to actuation of thephase A vehicle detectors D1, D2.

As will become evident from the description that follows, phase controlunit A includes various TIMER cir-, cuits, NOR circuits, AND circuits,OR circuits, and AND (A.C.) circuits. To facilitate the understanding ofthis invention, each of these circuits is briefly explained below.

TIMER CIRCUIT.This is a static, solid state means timing circuit havingan input circuit and an output circuit. Upon application of the groundpotential signal, known as a (0) signal, the timer commences its timingfunction and upon completion thereof develops at its output circuit apositive potential signal, known as a (1) signal.

NOR CIRCUIT.-This is a static, solid state means circuit having one ormore input circuits and one output circuit. A (0) signal is present atits output circuit whenever a (1) signal is applied to any of its inputcircuits. If a (0) signal is present on all of its input circuits, a (1)signal is present on its output circuit.

AND CIRCUIT.This is a direct current static, solid state means circuithaving two or more input circuits and one input circuit. A (1) signal ispresent at its output circuit so long as all of its input circuitsreceive a (1) signal. If a (0) signal is present at any of its inputcircuits, a (0) signal is present at its output circuit.

OR CIRCUIT.This is a static, solid state means circuit having two ormore input circuits and one output circuit. A 1) signal is present atits output circuit so long as any of its input circuits receive a (1)signal.

AND (A.C.) CIRCUIT.-This is a static, solid state means circuit, such asa transformer, having two input circuits and an output circuit whichserves to develop an alternating current output signal at its outputcircuit only when one of its inputs is connected to ground potential andthe other of its inputs is connected to the hot side of an alternatingcurrent voltage source.

STEP SWITCH Step switch SS preferably takes the form of an eight bank,eleven position step switch. If desired, the step switch may take theform of an electronic ring counter having the capability of cyclicallystepping through eleven positions. As is well known to those skilled inthe art, step switch SS cyclically steps through eleven positions,during which various circuits are completed by means of load relays LRfor energizing the traflic signal lights S. Various load relaycombinations may be made in accordance with a trafiic engineersschedule. From FIG. 4 it will be noted that step position Nos. 1, 2, 3,4, 5, 6, 7, 8, 9, 10 and 11 are respectively the special clearance No.2, minimum and density initial, green dwell, passage time and timewaitingminimum lull, vehicle clearance No. 1, special clearance No. 1,green No. 2, green, dwell, vehicle clearance N0. 2, red dwell No. 1, andred dwell No. .2 intervals. As will be noted in the description whichfollows, the phase unit illustrated in FIG. 3 may be a single phase unit(option 2) for controlling a single trafiic actuated phase, or may beused as a semiactuated, two phase traffic controller (option 1) forcontrolling main street in accordance with a pretimed schedule and crossstreet traffic flow in accordance with traffic demand. The phasecontroller may be converted to a semiactuated traflic controller byopening normally closed switches SW-l, SW-2, SW-3, SW- t, SW-S andclosing normally open switches SW-6, SW-7. For semiactuated operation(option 1, see FIG. 4), step switch intervals 10, 11 and 1 through 6 maybe the main street red (stop) period, intervals "7 and 8 may be the mainstreet green (go) period, and interval 9 may be the main street amber(caution) period. Also, step switch positions 6 through 11 and 1 may hethe cross street red period, positions 2 through 4 may be the crossstreet green period, and position 5 may be the cross street amberperiod. With switches SW-l through SW-7 in a position as shown in FIG.3, the circuit serves as a single phase, fully actuated, phase controlunit (option 2, see FIG. 4) during which step positions 10, 11 and Iserve as the actuated phase red (stop) period, step positions 2 through8 serve as the actuated phase green (go) period, and step position 9serves as the actuated phase amber (caution) period.

NORMAL TIMER Normal timer T1, like timers T2, T3, T4 and T5, generallycomprises a linear ramp function generator 30 and a differentialamplifier circuit serving as a comparator circuit 32. Generator 30includes a DC. amplifier 34 and a negative feedback capacitor 36.Briefly, upon application of a (0) signal to the input circuit ofgenerator 30, an output voltage V appears at its output circuit, whichpotential linearly increases in value with elapsed time, as shown by thewave form adjacent generator 30 in FIG. 3. The comparator 32 serves tocompare the value of the linearly increasing output voltage V with areference voltage V and develop a positive direct current voltage outputsignal, known as (1) signal, when the value of the two potentials issubstantially equal.

The reference voltage V applied to one of the input circuits ofcomparator 32 is obtained from one of five potentiometers 38, 40, 42, 44and 46. Each of the potentiometers has its resistance connected betweenground and the B+ voltage supply source through contacts on step switchSS. Accordingly, it is appreciated that the time delay required for theoutput voltage V of generator 30 to reach 7 the value of the referencevoltage V is dependent on the adjustment of the particular potentiometerin effect during the appropriate step position.

As discussed above, the various potentiometers 38, 40, 42, 44 and 46 areconnected through step switch contacts to the B+ voltage supply source.As is well known to those skilled in the art, each time that a stepswitch is energized, it steps one step to close one switch in each bankuntil the step switch is stepped to the next step posimally open switchcontacts on the eight banks in step position. Thus, for example, in stepswitch position 6 all nortion 6 are closed. Reference is now made topotentiometer 38 which has its resistance portion connected betweenground and the B+ voltage supply source through normally open stepswitch contacts located at bank 6, position I, referred to in thedrawings as SS6-1. Similarly, potentiometer 40 is connected to the B+voltage supply source through step switch contacts at bank 6, position2, SS62. Similarly, potentiometers 42, 44 and 46 are respectivelyconnected to the B+ voltage supply source through step switch contactsSS6-5, 556-6 and 556-9. It will be noted that these step switches areclosed at different positions of the step switch, no two being closed atthe same time. Thus, potentiometer 38 serves to adjust the time durationof special clearance No. 2 interval. Potentiometer 40 serves to adjustthe time duration of the minimum initial interval, potentiometer 42serves to adjust the time duration of vehicle clearance No. l interval,potentiometer 44 serves to adjust the time duration of special clearanceNo. 1 interval, and potentiometer 46 serves to adjust the time durationof a special clearance No. 2 interval. These step switch positions andtraffic intervals are illustrated in the chart of FIG. 4.

The input circuit of ramp function generator 30 is connected through apotential divider 48 to the B+ voltage supply source, as well as througha normally open interrupter contact S.S.INT.A to the 13+ voltage supplysource. Interrupter contacts A are located on the step switch andmomentarily close each time that the step switch is stepped from oneposition to the next. Thus, each time the step switch is actuated a 1)signal, i.e., B+ voltage, is applied to the input circuit of generator30 to reset the generator so that its output voltage V is referenced toground prior to commencing a timing operation.

The input circuit of the normal timer T1, taken at the input ofgenerator 30, is connected to the output circuit of a NOR circuit 50,which, in turn, has its input circuit connected to a source ofalternating current voltage L4 through an AC. to DC. converter 52. Thealternating voltage source L4 is preferably the hot side of analternating current voltage source, which has its other side connecteddirectly to ground. The ground side of the alternating current voltagesource will hereinafter be referred to either as ground or the L1voltage supply source. The converter 52 serves to convert thealternating current voltage into a positive potential known as a (1)signal for application to NOR circuit 50 so that so long as there is nodisruption in the voltage source L4, a (1) signal is applied to theinput circuit of NOR circuit 50, whereupon a (0) signal is applied fromthe output circuit of NOR circuit 50 to the input circuit of timer T1.The output circuit of timer T1, as taken at the output circuit ofcomparator circuit 32, is connected to the input circuit of an ORcircuit 54, having its output circuit connected to the input circuit ofan AND circuit 56. The output circuit of AND circuit 56 is connected toan input circuit of an OR circuit 58 having its output circuit connectedto the input circuit of another AND circuit 60. The output circuit ofAND circuit 60 is connected to ground through relay coil CR4-C of acontrol relay CR4.

VARIABLE INITIAL TIMER The variable initial timer T2 is substantiallyidentical to normal timer T l and, accordingly, like components areidentified in FIG. 3 with like reference characters. The

variable voltage V for comparator circuit 32 of timer T2 is taken from avoltage divider 62 connected between ground and the B+ voltage supplysource. The output circuit of the timer, as taken from the comparatorcircuit 32, is connected to an input circuit of AND circuit 56. Theinput circuit of timer T2 is connected to a B+ voltage supply sourcethrough a START circuit 64 and normally open step switch contacts SS6-Zat step switch bank 6, position 2. The input circuit of timer T2 is alsoconnected to the output circuit of a NOR circuit 66, which in turn hasits input circuit connected to the output circuit of AC. to D.C.converter 52. The variable initial timer serves to time a variableperiod of time in accordance with the number of actuations of phase Avehicle detectors D1, D2 and this function is provided by means of atime add circuit 68 connected to the input circuit of amplifier 34. Thetime add circuit is adjusted by a potentiometer 6 and has its inputcircuit connected to the B+ voltage supply source through normally openrelay contacts CR1-2 of relay CR1, and step switch normally opencontacts 856-1, 10, 11 so that whenever contacts CRl-Z are closed,during step positions 1, 10 and 11, B+ potential is applied to the timeadd circuit. Preferably, the variable initial timer is set so that itprovides a time increment between one and five seconds for each vehicleactuation.

PASSAGE TIME TIMER The passage time timer T3 is substantially identicalto the normal timer T1 and, accordingly, like components are identifiedby like reference numerals in FIG. 3. The passage time timer serves uponactuation to time a passage time, otherwise known as a unit extensiontime, which is the time required for a vehicle to traverse the distancefrom the phase A vehicle detectors D1, D2 to the stop line SL at theintersection (see FIG. 1). This time is normally set in the range from 0to 30 seconds, according to a traflic engineers schedule. The referencevoltage V for comparator circuit 32 of timer T3 is obtained from anadjustable passage time potentiometer 68. The output circuit of thetimer is taken from the output circuit of comparator 32 and is connectedto the input circuit of an AND circuit 70, having a second input takenfrom the B-lvoltage supply source through normally open step switchcontacts SS6-4. The output circuit of AND circuit 7% is connected to theinput circuit of OR circuit 54.

The input circuit of timer T3, as taken at the input circuit of the rampfunction generator 30, is connected to the output circuit of an ORcircuit 72. The input circuit of OR circuit 72 includes one inputconnected to the output circuit of NOR circuit 74, which in turn has itsinput circuit connected to the output circuit of the AC. to DC.converter 52. A second input circuit of OR circuit 72 is connected tothe output circuit of a NOR circuit 76, which in turn has its inputcircuit connected through an AC. to DC. converter 78 to the L4 voltagesupply source by means of normally open step switch contacts SS12, 3, 4.A third input circuit of OR circuit 9. A system for monitoring andadjusting power de- CR1-3 of relay CR1, to the B+ voltage supply source,through normally closed relay contacts CR32 of relay CR3.

EXTENSION LIMIT AND GREEN NO. 2 TIMER The extension limit and green No.2 timer T4 is substantially identical to the normal timer T1 and,accordingly, like components are identified with like referencecharacters in FIG. 3. The reference voltage V for the comparator circuit3.2 of timer T4 is obtained in step positions 2, 3 and 4 from the B+voltage supply source through potentiometer 80 and normally open stepswitch contacts 586-2, 3, 4. In step position 7, the reference voltage Vis obtained from the 13+ voltage supply source through potentiometer 82and normally open step switch contacts SS67. Potentiometer 8% serves toadjust the maximum duration of the extension limit period andpotentiometer 82 serves to adjust the time duration of the green No. 2interval (see FIG. 4).

The input circuit of timer T4, as taken at the input circuit of linearramp function generator 3 0, is connected to the output circuit of aNOLR circuit 84, having its input circuit connected to the outputcircuit of an AND circuit 86. One input circuit to AND circuit 86 isconnected to the B+ voltage supply source through normally open stepswitch contacts SS6 -7. The other input circuit for AND circuit 86 isconnected through an A.C. to D-.C. converter 88 to the alternatingcurrent voltage supply source L4.

The input circuit of timer T4 is also connected to the output circuit ofa NO R circuit 90, having its input circuit connected to the outputcircuit of an AC. to DC. converter 92. The input circuit of theconverter 92 is in turn connected to the output circuit of an AND (A.C.)circuit 94. AND circuit 94 may take the form of a transformer having itssecondary winding connected to converter circuit 92 and its primarywinding serving as an input circuit, with one end of the primary windingbeing connected to the alternating current voltage source L4 and theother end of the primary Winding being connected to ground through stepswitch contacts SSS2, 3, 4, a normally closed switch SW-3 and, in phaseunit B through normally open relay contacts CR2-3 (which correspond withthe like numbered contacts in phase unit A), and thence through thephase B step switch contacts SS7-10, 11. This portion of the circuitryof phase unit B is shown in FIG. 3 only for purposes of clarifying themanner of interconnection of phase units A and B.

The output circuit of timer T4, taken at the output circuit ofcomparator 32, is connected to one input circuit of an AND circuit 96,having another input circuit connected to the B+ voltage supply sourcethrough normally open switch contacts 586-7. The output circuit of ANDcircuit 96 is connected to an input circuit of OR circuit 58. The outputcircuit of timer T4 is also connected to the input circuit of anotherAND circuit 98, having a second input circuit connected to the B+voltage supply source through normally open step switch contacts 586-2,3, 4; The output circuit of AND circuit 98 is connected to one inputcircuit of an OR circuit 100. The output circuit of OR circuit 100 isconnected to ground through relay coil CR3-C of relay CR3.

TIME WAITING-MINIMUM LULL TIMER The time waiting-minimum lull timer T5is substantially identical to the normal timer T1 and, accordingly, likecomponents in both circuits are identified with like referencecharacters in FIG. 3. A major distinction, however, between timer T5 andthe normal timer T1 is that the generator 30' of timer T5 is thecomplement of generator 30 in timer T1. That is, as will be noted from acomparison of the wave forms associated with the circuitry of timer T1or T5, the value of output voltage V of timer T1 linearly increases in apositive direction with elapsed time, whereas the value of outputvoltage V of timer T linearly decreases toward ground potential withelapsed time. The reference voltage V for comparator circuit 32 of timerT5 is taken from the output circuit of generator 30 in timer T3 so thatthe reference voltage V is equal to the value of output voltage V ofgenerator 30 in timer T3. Accordingly, timer T5 serves to compare thelinearly decreasing voltage V from generator 30 with the linearlyincreasing reference voltage V taken from the generator 30 of timer T3.

The input circuit of timer T5, as taken at the input circuit ofgenerator 30, is connected through a time waiting adjustablepotentiometer 102 to the junction of a potential divider 104. Thepotential divider 104 is connected between the wiper arm ofpotentiometer 68 of timer T3, and the wiper arm of a minimum lulladjustable potentiometer !106, which in turn is connected between groundand the B+ voltage supply source.

The input circuit of timer T5 is also connected to the output circuit ofa NOR circuit 108, having its input circuit connected to the outputcircuit of an AC. to DC. converter 112. Converter '112 is connected tothe output circuit of an AND (A.C.) circuit 110. One of the inputcircuits of AND (A.C.) circuit 110 is connected to power source L4 andthe other of its input circuits is connected through normally open stepswitch contacts SS84, normally closed switch SW-3, and in the phase Bcontrol unit through normally open relay contacts CR2-3 and, thence,through step switch contacts SS7-10, 11 to ground.

RELAY CIRCUITS To some extent, the description given hereinabove withrespect to the timers T1, T2, T3, T4 and T5 has included description asto the circuit interconnection with relays CR1, CR2 and CR3. Relay CR1may be termed as the vehicle detection relay and includes relay coilCR1-C which is connected between a 12 volt alternating current voltagesource, labeled as 12 V. AG. in FIG. 3, and ground through phase Adetectors D1, D2 which are illustrated in the circuit as a normally openswitch. Relay CR1 includes normally open relay contacts CR1-1, CR1-2 andCR1-3. These contacts have been discussed hereinbefore with respect totheir interconnection with the timer circuits. In addition to theinterconnections previously described with respect to the timer, it willbe noted from FIG. 3 that contacts CR1-1 are connected to ground throughrelay coil CR2-C of memory relay CR2. Relay CR2 also includes normallyopen relay contacts CR2-2 and CR2-3. Relay CR3, which includes relaycoil CR3-C connected between the output circuit of OR circuit andground, also includes normally open relay contacts CR3-1 and normallyclosed relay contacts CR3-2. In addition, the relay circuits alsointerconnect with a recall switch SW-10, which includes a pair of gangedmovable contacts 116 and 118. Movable contacts 116 and 118 are fourposition contacts, and may be positioned in either one of fourpositions; namely, maximum, recall, olf, and eX- ternal memory. In theoff position, contact 116 serves together with relay contacts CR2-2 toprovide a shunt circuit across normally open detector relay contactsCR1-1. Thus, whenever relay coil CR1-C is energized, to energize relaycoil CR2-C (when in step positions 1 and 5 through 11), relay contactsCR2-2 close to provide a shunt path across contacts CR1-1 to maintainrelay coil CR2-C energized. With switch SW-10 in its recall position,movable contact 116 connects relay coil CR2-C between ground and thealternating current voltage source L4 (in step positions 1 and 5 through11) to maintain the memory coil in a constant recall condition. Whenswitch SW-10 is in its maximum position, movable contact 118 connectsdetector relay coil CR1-C between ground and the 12 volt alternatingcurrent voltage source so as to constantly energize the detector relaycoil. When switch SW-10 is in its external memory position, the memoryfunction is performed by external memory means such as a presencedetector which, as described hereinbefore, provides an output signal solong as a vehicle is present within its zone of influence. In additionto the foregoing, it will be noted that relay contacts CR3-1 serve, whenclosed, to provide a shunt between voltage source L4 and relay contactsCR1-1. Also, memory relay contacts CR2-3 serve, when closed during steppositions 10 and 11, to provide a vehicle calling signal, representativethat a vehicle on phase A demands right-of-way movement through theintersection, to the phase B phase control unit through normally closedswitch SW-3.

STEP SWITCH DRIVER CIRCUIT The step switch driver circuit includes relaycoil CR4-C, of relay CR4, in the output circuit of AND circuit 60. RelayCR4 includes a set of normally open contacts CR4-1 which serve toconnect a step switch driver coil CRS-C between the alternating currentvoltage source L4 and ground through diode 120. The step switch SS isdriven one step, in a manner well known in the art, in response to eachenergization of driver coil CRC. The step switch is driven from stepposition 3 to step position 4 when a circuit is completed across coilCRS-C from the alternating current voltage source L4 through normallyclosed interrupter contacts CR5INT-C, off normal contact 122, normallyopen step switch contacts SSS-3, normally closed switch SW3, normallyopen relay contacts CR23 (in phase unit B) and normally open phase Bstep switch contacts SS710, 11 to ground. The off normal contacts 122are controlled by the step switch and are normally open, except in stepposition 3. The normally closed interrupter contacts CRS-INT-C arecontrolled by driver coil CRS-C and are open during the period that thecoil is energized.

The input circuit of AND circuit 60 is connected to the output circuitof a NOR circuit 124. One of the input circuits of NOR circuit 124 isconnected to a source of L1 power (ground) except during step positions3 and 8.

The step switch SS is stepped from its step position 3 to its stepposition 4 by the circuit described above with respect to the off normalcontacts 122 and the interrupter contacts CR5INTC. The followingdescription is given with respect to the circuit that is used forstepping the step switch SS from step position 8 to step position 9.This circuit includes a path taken from an input circuit of another NORcircuit 125, having its output connected to relay coil CR4C, throughnormally closed switch SW-5, normally open step switch contacts SSS-8and, thence, through normally closed switch SW3 and into the phase Bcontrol unit through normally open relay contacts CR23 and step switchcontacts 557-10, 11 to the L1 power source, i.e., ground. Accordingly,it is seen that the step switch cannot be stepped out of its steppositions 3 or 8 unless relay contacts CR2-3 in the phase B control unitare closed, representative of a vehicle demanding right-of-way movementon phase B. A second input circuit for NOR circuit 124 is taken throughnormally open switch SW6 (which is closed only for semiactuatedoperation) and thence to the junction between normally closed switchSW-4 and relay contacts CR23.

In local controller LC, which includes phase units A and B forcontrolling phase A and phase B trafiic flow, the phase unit associatedwith the traffic phase to which a stop signal is displayed normallydwells in red dwell No. 1 interval, at step position (see FIG. 4). Whenthe phase unit associated with the phase to which a go signal isdisplayed is stepped from step position 8 to step position 9, it isdesirable that the other phase unit be stepped from step position 10 tostep position 11. Similarly, when the phase unit in control is steppedfrom step position 9 to step position 10, the other phase unit isstepped from red dwell No. 2 interval, at step position 11, to stepposition 1. The circuit for accomplishing this function is describedbelow. Normally closed switch SW-l is connected from the junction ofcoil CRS-C and relay contacts CR41 to normally open phase A step switchcontacts SS4-8, and thence to phase B step switch contacts SS410.Similarly, switch SW-l is connected through phase A step switch contactsSS4-9, 11, and thence to phase B step switch contacts SS4-9, 11. SwitchSW-Z serves to connect the junction of switch SW1 and coil CRS-C throughphase A step switch contacts SS4-10 to the phase B step switch contactsSS4-8. Also, switch SW-2 is connected through phase A step switchcontacts 854-9, 11 to phase B step switch contacts 854-9, 11. Theoperation of these circuits will be appreciated from the detaileddescription which follows.

OPERATION Phase A, step position 10 A cycle of operation for phase unitA of local controller LC commences, for example, when phase unit A is inits red dwell No. l interval, i.e., step position 10.

When phase B is stepped from its step position 8 to its step position 9,L1 power is applied from phase unit B through now closed step switchcontacts 534-8, through now closed phase A step switch contacts 584-10,and thence through switch SW-2 to complete an energizing circuit forphase A step switch coil CRS-C. Accordingly, this steps the step switchSS in phase unit A from step position 10 to step position 11, the phaseA red dwell No. 2 interval. Simultaneously therewith, the phase B stepswitch is stepped from its step position 8 to its step position 9, aswill be appreciated from the description which follows with reference tophase unit A.

Phase A, Step position 11 After phase unit B has timed its vehicleclearance No. 2 interval, i.e., step position 9, L1 power is appliedfrom phase unit B through its now closed step switch contacts 554-9,through the now closed phase A step switch contacts 584-11, and thencethrough switch SW-2 to complete an energizing circuit for phase A stepswitch coil CRS-C. Thus, the phase A step switch SS is stepped from itsstep position 11 to step position 1, the phase A special clearance No. 2(stop) interval. As will be appreciated from the description whichfollows, phase unit B is also stepped from its step position 9 to itsstep position 10, the red dwell No. 1 interval, where the phase B unitdwells until it becomes trafi'ic actuated. Phase unit A is now incontrol.

Phase A, Step position 1 In step position 1, phase A normal timer T1times a fixed special clearance No. 2 interval, illustrated as a red orstop interval in FIG. 4. The time duration of this interval isdetermined by the value of the reference voltage V applied to comparator32, as adjusted by potentiometer 38. As the step switch was stepped intostep position 1, step switch interrupter contacts SS-INT-A momentarilyclosed to apply B+ potential, i.e., a (1) signal, to the input circuitof timer T1. This resets the timer so that as the switch reopens anenergizing (0) signal is applied to the timer. In the event that the L4power source fails, a (1) signal is applied from NOR circuit to theinput circuit of timer T1, to constantly maintain the timer reset. Inthe absence of such power failure, however, timer T1 commences itstiming function as the step switch steps to position 1. Accordingly, theoutput voltage V of generator 30 in timer T1 linearly increases untilsuch time that the value of voltage V is substantially that of thereference voltage V whereupon a (1) signal is applied from the outputcircuit of comparator 32 to the input circuit of OR circuit 54. The ORcircuit applies a (1) signal to the input circuit of AND circuit 56. TheAND circuit 56, however, requires a second (1) input signal from theoutput circuit of comparator circuit 32 of timer T2 before it appliesa 1) signal to OR circuit 58. As shown by the wave form associated withgenerator 30 of timer T2, the output voltage V is normally set so thatit is above ground potential, i.e., close to B+ potential. Accordingly,in the absence of timer T2 being reset, an output signal, i.e., a (1)signal, is applied from the output circuit of comparator 32 of timer T2to the AND circuit 56. AND circuit 56 applies a (1) signal through ORcircuit 58 to the input circuit of AND circuit 60. AND circuit 60, inturn, receives a second (1) signal from the output cir cuit of NORcircuit 124, except during step positions 3 and 8. Thus, a (1) signal isapplied from the output circuit of AND circuit 60 to energize controlrelay coil CR4-C. This closes relay contacts CR4-1, completing anenergizing circuit for step switch coil CRS-C. The step switch SS stepsfrom its step position 1 to step position 2, the minimum and densityinitial interval.

13 Phase A, step position 2 As shown in FIG. 4, step position 2 is a goor green signal interval for phase A traific. At the commencement ofthis interval circuits are completed for energizing normal timer T1, theextension limit timer T4, the variable initial timer T2, the passagetime timer T3, and relay coil CR3-C. The operation with respect to eachthese circuits is described below.

Upon advancement into the minimum initial interval, timer T1 is reset bystep switch interrupter contacts SS- IN'T-A and the timer then commencesits timing function. The reference voltage V is obtained frompotentiometer 40 during step position 2 since normally open steppingswitch contacts 856-2 are now closed. When the output voltage V ofgenerator 30 is substantially equal to the reference V a (1) signal isapplied through OR circuit 54 to the input circuit of AND circuit 56.AND circuit 56, however, does not apply a (1) signal to OR circuit 58until a (1) signal is developed by the output circuit of variableinitial timer T2. In step position 2, START circuit 64 associated withtimer T2 is initiated to actuate timer T2 to commence its timingfunction. The minimum value of voltage V is adjusted by the time addcircuit 68 so as to vary the time required for the output voltage V tobe substantially equal to the reference voltage V The greater theminimum value of voltage V the lesser the time required to obtain anoutput (1) signal from timer T2 and, conversely, the lesser the minimumvalue of voltage V the greater the time required for timer T2 to developan output (1) signal. The time add circuit 68 receives a B--|- signalduring step positions 1, 10 and 11 for each closure of vehicle de tectorrelay contacts CR12. Accordingly, the variable initial time isproportionally increased in accordance with the number of vehiclesdetected during the preceding period that a stop signal was displayed tophase A trafiic. The variable initial timer may be set by potentiometer69 to provide approximately five seconds for each vehicle detection.When timer T2 completes its timing function, it applies a (1) signal tothe input circuit of AND circuit 56, whereupon the AND circuit applies a(1) signal through OR circuit 58 to the input circuit of AND circuit 60.Since a (1) signal is applied to AND circuit 60 from the output circuitof NOR circuit 124, except during step positions 3 and 8, a (1) signalis applied to energize control relay coil CR4-C, thereby completing anenergizing circuit for step switch driver coil CR5C. Thus, the stepswitch SS is stepped from step position 2 to step position 3, the greendwell interval.

At the commencement of step position 2, a circuit is also completed forenergizing the passage time timer T3. More particularly, in steppositions 2, 3 and 4 a circuit is completed from the alternating currentvoltage source v L4 through step switch contacts SS12, 3, 4, and thencethrough the AC. to DC. converter 78 for developing a (1) signal forapplication to NOR circuit 76. Accordingly, NOR circuit 76 applies a (0)signal through OR circuit 72 to the input circuit of timer T3. Also, solong as there is not a failure of L4 power, a (0) signal is applied byNOR circuit 74 through OR circuit 72 to the input circuit of timer T3.Thus, the passage time timer commences its timing function so as to timeat least one passage time, as adjusted by potentiometer 68. The passagetime timer may be reset by vehicle actuations in phase A, since for eachactuation relay coil CRl-C is energized to close its contacts CR1-3.Closure of contacts CR1-3 applies a (1) signal from the B+ voltagesupply source through normally closed relay contacts CR3-2 to OR circuit72. This momentary application of a (1) signal through 0R circuit 72resets timer T3 so that it commences to time a second passage time. Whenthe passage time timer completes its timing function, a (1) signal isdeveloped at its output circuit for application to AND circuit 70.However, a (1) signal is not applied from the output circuit of ANDcircuit 70 to the input circuit of OR circuit 54 in any step switchposition other than step switch position 4. Accordingly, if passage timetimer completes its timing function in interval 2 or .3, this will notactuate the step switch SS.

During light traffic conditions, the variable initial timer T2 may timeout before the normal timer T1 completes its timing function. Duringheavy tramc conditions, however, the variable initial timer T2 mayrequire considerable time to complete its timing function after thenormal timer T1 has timed out. Thus, the phase A traflic would maintainright-of-way to the detriment of the phase B trafiic. The extensionlimit portion of timer T4 serves to time a maximum period of go time forphase A traflic, after a vehicle on phase B has registered its demandfor right-of-way movement through the intersection. More particularly,any time during phase A step positions 2, 3 and 4 a circuit is completedfor energizing time T4 when a vehicle actuation has occurred on phase B.Thus, when relay contacts CR2-3 in phase B become closed, representativeof a vehicle actuation in phase B during phase B step position 10 or 11,L1 power is applied through the phase B step switch contacts SS7- 10,11, the now closed relay contacts CR2-3 in phase B, and thence to thephase A unit through switch SW4, through phase A step switch contactsSSS-2, 3, 4, to AND (A.C.) circuit 94. So long as L4 power has notfailed, AND (A.C.) circuit 94 applies an AC. signal to the AC. to DC.converter 92. Circuit 92, in turn, applies a (1) signal to the inputcircuit of NOR circuit 90, which, in turn, applies a (0) signal to theinput signal circuit of timer T4 so that timer T4 may commence itstiming function. The time duration of the extension limit period isdetermined by the adjusted value of the reference voltage V which duringstep positions 2, 3 and 4 is obtained from potentiometer 80. When theextension limit portion of timer T4 completes its timing function, a (1)signal is applied from its output circuit to the AND circuit 98. Duringstep positions 2, 3 and 4, AND circuit 98 applies a (1) signal throughOR circuit 100' to energize relay coil CR3-C of relay CR3. This, inturn, opens normally closed relay contacts CR3-2, thereby preventingfurther vehicle actuations on phase A from resetting the passage timetimer T3. Accordingly, the passage time timer completes timing a passagetime and then develops a (1) signal for application to AND circuit 70.If this occurs during step position 2 or 3, then as soon as the stepswitch is stepped to step position 4, a 1) signal is applied by ANDcircuit 70 through OR circuit 54 to AND circuit 56.

Phase A, step position 3 When the step switch is stepped from stepposition 2 to step position 3, the phase A control unit is in its greendwell interval. This is not a timed interval. In order for the stepswitch to he stepped from step position 3 to step position 4, a vehicleactuation must occur in phase B. When a vehicle actuation has occurredin phase B, relay contacts CR2-3 in the phase B control unit are closedand L1 power is supplied through phase B step switch contacts 887-10, 11through the now closed contacts CR2-3, and thence through switch SW-3 tophase A step switch contacts SS8-3, through the off normal con.- tacts122, which are closed during step position 3, through the interruptercontacts CRS-INT-C to complete an energizing circuit for step switchdriver coil CR5C. The step switch steps from step position 3 to stepposition 4. Accordingly, it is seen that if the phase B vehicleactuation took place during the phase A step position 2, the phase Agreen dwell interval would be substantially eliminated. Otherwise, thephase A control unit dwells in its green dwell interval until such timeas a vehicle actuation occurs on phase B.

Phase A, step position 4 In step position 4, the phase A passage timeand time waiting-minimum lull period, the step switch will be stepped tostep position 5 as soon as the passage time timer completes its timingfunction so that AND circuit 70 provides a (1) signal through OR circuit54 to AND circuit 56. As discussed hereinabove, the passage time timerwill be forced to complete its timing function in the event that theextension limit portion of timer T4 completes its timing function. Thisoccurs because when the extension limit timer completes its timingfunction, it develops an output signal which disables the reset featureof the passage time timer by energizing relay coil CR3-C, causingcontacts CR32 to open. However, the time waitingminimum lull timer T5also serves, during step position 4, to energize relay coil CR3C andthus disable the reset feature of the passage time timer. During stepposition 4, L1 potential is applied from phase unit B through phase Bstep switch contacts SS710, 11 and closed relay contacts CR2-3,representative of a phase B vehicle detection, and thence through switchSW3, and through phase A step switch contacts SS84 (A.C.) circuit 110.So long as L4 power has not failed, AND (A.C.) circuit 110 applies analternating current voltage signal to converter circuit 112. Convertercircuit 112 applies a signal to NOR circuit 108 which, in turn, appliesa (1) signal to the input circuit of timer T5, causing the timer tocommence its timing function. Since ramp function generator 30' is thecomplement of generator 30 of the normal timer T1, the output voltage Vof generator 30' linearly decreases, as shown by the wave formassociated with timer T5. The reference voltage V for comparator circuit32 of timer T is the output voltage V of generator in the passage timetimer T3. When the output voltage V of generator 30 is substantiallyequal to the reference V comparator 32 of timer T5 develops a (1) signalfor application through OR circuit 100, energizing relay coil CR3-C.This opens relay contacts CR3-2, preventing further reset of passagetime timer T3. Accordingly, the passage time timer T3 completes itstiming of a passage time and applies a (1) signal to AND circuit 70. Itis to be appreciated that it is possible for timer T 5 to time out afterthe extension limit portion of timer T4 and, accordingly, the extensionlimit time will control the point in time that the reset feature of thepassage time timer is disabled. A (1) signal is applied through ORcircuit 54 to AND circuit 56. Since the variable initial timer haspreviously timed out, a (1) signal is also applied from timer T2 to ANDcircuit 56, whereupon the AND circuit applies a (1) signal through ORcircuit 58 to AND circuit 60. Since AND circuit 60 receives a (1) signalfrom NOR circuit 124, except during step positions 3 and 8, a (1) signalis also applied from the output of AND circuit 60 to energize controlrelay coil CR4C. This closes relay contacts CR41 to complete anenergizing circuit for step switch coil CRS-C. Accordingly, step switchSS steps from step position 4 to step position 5, the phase A vehicleclearance No. 1 interval.

Phase A, step position 5 The phase A vehicle clearance No. 1 interval isa go interval for phase A and is timed by normal timer T1. The timeduration of this interval is dependent on the value of the referencevoltage V applied to comparator 32 of timer T1, which voltage, in turn,is adjusted by potentiometer 42. When the output voltage V of generator30 of timer T1 is substantially equal to the reference voltage V a (1)signal is applied from the output circuit of timer T1 through OR circuit54 to the input circuit of AND circuit 56. Since a (1) signal is appliedfrom the output circuit of the variable initial timer T2 to the ANDcircuit 56, a (1) signal is applied through OR circuit 58 to AND circuit60. Since a (1) signal is also applied to the AND circuit 60 from theoutput cir cuit of NOR circuit 124, except during step positions 3 and8, a (1) signal is also applied from the output circuit of AND circuit62 to energize relay coil CR4C. This closes relay contacts CR4-1 tocomplete an ener- 16 gizing circuit for step switch driver coil CRS-C.Thus, step switch SS steps from step position 5 to step position 6, thephase A special clearance No. 1 interval.

Phase A, step position 6 The phase A special clearance No. l interval isa go interval for phase A, as indicated in FIG. 4. This interval istimed by the normal timer T1. The duration of the interval is dependenton the value of the reference voltage V as adjusted by potentiometer 44.When the output voltage V of generator 30 is substantially equal to thereference voltage V the comparator circuit 32 of timer T1 applies a (1)signal through OR circuit 54 to the AND circuit 56. Since the variableinitial timer T2 has completed its timing circuit, its comparatorcircuit 32 also applies a (1) signal to AND circuit 56. Accordingly, ANDcircuit 56 applies a (1) signal through OR circuit 58 to AND circuit 60.Since a (1) signal is also applied to AND circuit 60 from the outputcircuit of NOR circuit 124, except during step positions 3 and 8, a (1)signal is applied from the output circuit of AND circuit 60 to energizecontrol relay coil CR4C. This closes relay contacts CR4-1 which, inturn, completes an energizing circuit for step switch driver coil CRS-C.Thus, the step switch SS steps from step position 6 to step position 7,the phase A green No. 2 interval.

Phase A, step position 7 The green No. .2 interval is a go interval forphase A, as indicated in FIG. 4, and is timed by the green No. 2 portionof timer T4. The time duration of this interval is dependent on thevalue of reference voltage V which, during step position '7, isdependent on the adjustment of potentiometer 82. In step position No. 7,a B+ potential is applied through step switch contacts SS6-7 to theinput circuit of AND circuit 86. In the absence of power failure ofalternating current voltage source L4, a (1) signal is also applied tothe AND circuit 86 from the AC. to DC. converter circuit 88. Thus, ANDcircuit 86 applies a (1) sginal to NOR circuit 84 which, in turn,applies a (0) signal to the input circuit of timer T4. Thus, timer T4commences its timing function and, when the output voltage V ofgenerator 30 is substantially equal to the reference voltage V a (1)signal is applied from the output circuit of comparator circuit 32 oftimer T4 to the input circuit of AND circuit 96. A (1) signal is alsoapplied to the input circuit of AND circuit 96 from the B+ voltagesupply source through step switch contacts SS6-7. Accordingly, ANDcircuit 96 applies a (1) signal through OR circuit 58 to the AND circuit60'. Since a (1) signal is also applied to the AND circuit 60 from theoutput circuit of NOR circuit 124, except during step positions 3 and 8,AND circuit 60 applies a (1) signal to relay coil CR4C. This closesrelay contacts CR4-1 for completing an energizing circuit for the stepswitch driver coil CRSC. Thus, the step switch SS steps from stepposition 7 to step position 8, the phase A green dwell interval.

Phase A, step position 8 The green dwell interval is not a timedinterval. The phase A control unit will dwell in this position untilsuch time as a vehicle actuation occurs on phase B. More particularly,it is possible that the trafllc actuation on phase B, which caused thephase A control unit to step from step position 3 has been lost, by thetime the unit is advanced to step position 8, as by a malfunction inequipment operation. Accordingly, so that stop signals are not displayedto all phases during this condition, phase A control unit remains instep position 8. If the phase B traflic actuation is still in effect, orat such time that a phase B trafiic actuation occurs, a circuit iscompleted for energizing the step switch driver coil CRS-C. Driver coilCRS-C is energized by a circuit which commences in phase unit B fromsource Ll through phase B step switch contacts SS7-10, 11, throughclosed relay contacts CR2-3, representative of a phase B trafiicactuation, through switch SWG, and then through phase A step switchcontacts SSS-8, switch SW-5 to NOR circuit 125. Thus, a (1) signal isapplied from the output circuit of NOR circuit 125 to energize relaycoil CR4-C. This closes relay contacts CR4-1 for completing anenergizing circuit for the step switch driver coil CR5C. Thus, the stepswitch SS steps from step position 8 to step position 9, the phase Avehicle clearance No. 2 interval.

Phase A, step position 9 The vehicle clearance No. .2 interval is acaution interval for phase A, as indicated by the chart in FIG. 4-, andis timed by normal timer T1. The duration of this interval is dependenton the value of the reference voltage V as adjusted by potentiometer 46.When the output voltage V of generator 30 is substantially equal to thereference voltage V the comparator circuit 32 of timer T1 applies a (1)signal through OR circuit 54 to AND circuit 56. Since the variableinitial timer T2 has completed its timing function, its comparatorcircuit 32 also applies a (1) signal to AND circuit 56. Accordingly, ANDcircuit 56 applies a (1) signal through OR circuit 58 to AND circuit 60.Since a (1) signal is also applied to AND circuit 60 from the outputcircuit for NOR circuit 124, except in step positions 3 and 8, a (1)signal is applied from the output circuit of AND circuit 60 to energizecontrol relay coil CR4-C. This closes relay contacts CR4-1, which, inturn, completes an energizing circuit for step switch driver coil CRS-C.Thus, the step switch S5 steps from step position 9 to step position 10,the phase A red dwell No. 1 interval.

As the step switch SS was stepped from step position 8 to step position9, ground potential, i.e., L1 power, was applied through relay contactsCR4-1, switch SW-l,

phase A step switch contacts 884-8, and thence through phase B stepswitch contacts $84-10 to complete an energizing circuit through phase Bswitch SW-2 and phase B step switch driver coil CRS-C. Accordingly, thissteps the phase B step switch SS from step position 10 to step position11, the phase B red dwell No. 2 interval.

Phase A, step position 10 The red dwell No. 1 interval is a stopinterval for phase A, as indicated by the chart in FIG. 4. The phase Aunit will dwell in step position 10 until it becomes traffic actuated.As the phase A step switch SS was stepped from step position 9 to stepposition 10, L1 power was applied through contacts CR4-1 through phase Aswitch SW4, phase A step switch contacts 884-9, and thence in phase Bunit through step switch contacts 884-11 and phase B switch SW-2 tocomplete an energizing circuit for the phase B step switch driver coilCRS-C. Thus, the phase B step switch is stepped from step position 11 tostep position 1, the phase B special clearance No., 2 (stop) interval.Phase unit B is now in control and will commence timing its intervalsNo. 1 and No. 2 and then dwell in its green dwell interval, i.e., phaseB step switch position No. 3, until it receives a call from phase Aunit, indicative of a traffic actuation in phase A. The sequence ofoperation for phase unit B is the same as that just described withrespect to phase unit A.

Although the invention has been described thus far in conjunction with atwo phase, full actuated trafiic control system including separate phaseunits A and B for controlling trafiic flow through an intersection oftrafiic actuated phases A and B, it is to be appreciated that theinvention may also be used in conjunction with a semiactuated, two phasecontrol system including a single control unit. More particularly, thephase unit A described thus far with respect to FIG. 3, may be convertedto a two phase, semiactuated trafiic controller. This conversion takesplace by merely opening switches SW-l, SW-2, SW-3, SW4 and SWS, andclosing switches SW6 and SW7. In addition to actuating the switches,suitable load relay changes should bemade so that step switch SSconnects both main street and cross street signal lamps to a source ofpower during the appropriate step switch intervals. Having made suchconversions, a typical trafiic interval versus step position may takethe form as shown in the chart of FIG. 4 (option 1) for a two phase,semiactuated controller. More particularly, it will be noted that stepswitch positions 10, 11 and 1 through 6 constitute a stop. period formain street trafiic, that step positions 7 and 8 serve as the mainstreet go period, and that step position 9 serves as the main streetcaution or amber period. Also, under these conditions, it will be notedthat step positions 6 through 11 and 1. serve as the cross street red orstop period, that step positions 2 through 4 serve as the cross streetgreen or go period, and step position 5 serves as the cross streetcaution or amber period. As is common in the art of trafiic control forsuch a two phase, semiactuated controller, the cross street serves asthe 'trafiic actuated phase and main street is the nonactuated traflicphase.

,The invention has been described in connection with a particularpreferred embodiment, but is not to be limited to save. Variousmodifications may be made without departing from the scope and spirit ofthe present invention as defined by the appended claims.

Having thus described our invention, we claim:

1. A trafiic controller for controlling the operation of an intersectiontraffic signal displaying at least go and stop signals to at least twointersecting traflic phases, at least one of said phases being a trafiicactuated phase and to which a said go signal display includes an initialinterval followed by a vehicle extension interval and which actuatedphase has vehicle detection means associated therewith for developing adetection signal for each detected vehicle, said controller includingfor each said actuated phase:

minimum initial timing means for timing a predetermined minimum gosignal initial interval and then developing a first signal;

variable initial timing means controlled by said associated detectionmeans for timing a variable go signal initial interval in accordancewith the number of vehicles detected by said detection means during thepreceding period of time that a stop signal was displayed to saidactuated phase and then developing a second signal;

vehicle extension timing means for timing a predetermined go signalvehicle extension interval and then developing a third signal;

starting means for concurrently energizing said minimum initial,variable initial, and vehicle extension timing means so that all of saidtiming means commence their timing functions at substantially the samepoint in time;

first AND circuit means for developing an initial interval terminationsignal only in response to concurrent occurrence of said first andsecond signals;

trafiic interval control means responsive to a said initial intervaltermination signal to terminate said go signal initial interval andallocate a said go signal vehicle extension interval;

second AND circuit means for developing a vehicle extension intervaltermination signal only when both said initial interval terminationsignal and said third signal have been developed; and,

said trafiic interval control means being responsive to a said vehicleextension interval termination signal to terminate a said go signalvehicle extension interval.

2. A trafiic controller as set forth in claim 1, including reset meanscontrolled by said associated detection means for resetting said vehicleextension timing means in response to each detection of a vehicle insaid actuated phase so that said vehicle extension timing means beginstiming another said vehicle extension interval.

3. A tratfic controller as set forth in claim 2, including extensionlimit timing means for timing a predetermined time limit for said gosignal display to said actuated phase and then developing a fourthsignal;

reset disabling means responsive to a said fourth signal for disablingsaid reset means, whereby said vehicle extension timing means completesits timing function and develops said third signal.

4. A traffic controller as set forth in claim 3, including secondstarting means for developing an energizing signal for energizing saidextension limit timing means.

5. A trafiic controller as set forth in claim 4, wherein said secondstarting means includes vehicle detection means associated with anotherof said phases, whereby said extension limit timing means is energizedonly in response to a vehicle detection occurring in another of saidphases.

6. A traffic controller as set forth in claim 5, including third ANDcircuit means coupling said first and second starting means with saidextension limit timing means.

7. A traffic controller as set forth in claim 1, wherein said controlleris a semiactuated two phase controller.

8. A traffic controller as set .forth in claim 1, wherein saidcontroller is a two or more phase traffic actuated controller andwherein for at least one of said phases said controller includes asemiactuated two phase controller having switching means for convertingsame to a single phase trafiic actuated control unit.

9. A traffic controller as set forth in claim 8, wherein said controllerincludes a said single phase trafiic actuated control unit for eachphase.

10. A traffic controller as set forth in claim 1, wherein each of saidtiming means includes generating means for generating a timing signalwhich progressively varies in value with elapsed time, and comparingmeans for comparing said timing signal with a reference signal anddeveloping an output signal when said timing signal and said referencesignal attain a predetermined relationship to each other.

11. A traffic controller as set forth in claim 10, including means forproviding said reference signal to said comparing means as a voltagepotential.

12. A traflic controller as set forth in claim 11, wherein said timingsignal is a voltage potential, and said comparing means includes adifferential amplifier for comparing said potentials.

13. A traffic controller as set forth in claim 11, wherein saidreference signal providing means is adjustable, whereby the time delaybetween energization of said generating means and development of a saidoutput signal by said comparing means is directly proportional to theadjusted value of said reference signal.

14. A traffic controller as set forth in claim 10, wherein saidgenerating means is a linear ramp function generating means fordeveloping said timing signal so that it progressively varies in valuein a linear manner with elapsed time.

15. A control system for controlling stop and go movement of movablemeans through an intersection of at least two flow paths of movement ofsaid movable means, at least one of said flow paths having detectionmeans associated therewith for detecting each said movable means in saidone path, said system having for at least said one path:

first timing means for timing a predetermined minimum period of movementtime along said one path for said movable means, and then developing afirst signal;

second timing means for timing a variable period of movement time alongsaid one path for said movable means in accordance wtih the number ofsaid movable means detected by said detection means during a precedingperiod of time that go movement through said intersection was denied tomovable means in said one path, and then develop ing a second signal;

third timing means for timing a predetermined go movement extensionperiod of time and then developing a third signal;

starting means for concurrently energizing said first,

second, and third timing means so that all of said timing means commencetheir timing functions at substantially the same point in time;

fiirst AND circuit means for developing an initial go movementtermination signal only in response to concurrent occurrrence of saidfirst and second signals;

movement control means responsive to a said initial go movementtermination signal to initiate termination of a first go movement periodthrough said intersection and allocate an extension go movement periodthrough said intersection;

second AND circuit means for developing an extension go movementtermination signal only when both said initial go movement terminationsignal and said third signal have been developed; and,

said movement control means being responsive to a said extension gomovement termination signal to terminate a said extension go movementperiod.

THOMAS B. HABECKER, Primary Examiner US. Cl. X.R.

